Hi I am adding air- conditioning to a lennox g-8 furnace . The fan only has one speed and the transformer is very old in this furnace. I have purchased a fan centre . I am just condering could I have put in a relay instead. Or is it just better to go with a fan centre considering that it has a new transformer and a relay in it already and will switch the fan in cooling mode . This unit also has a standing pilot does the pilot need to be lit to send a millivolt signal back to the gas valve in order to send 24v through the control circuit. Thanks

No it should not. Follow the directions that came with the fan center. Your blower motor may not have enough horse power to move enough air for the new A/C. I would recommend a professional to braze the lines and make the final connections and check out.